1. Field of the Invention
This invention relates to a contact switch assembly, more particularly to a contact switch assembly having stationary conductors, one of which holds a spring-loaded contact plate to selectively contact the other conductors.
2. Description of the Related Art
Referring to FIG. 1, a conventional contact switch, such as a microswitch, is shown to comprise a casing 11, a common conducting unit including a conductor body 12 and an elongated movable contact plate 13 mounted on the conductor body 12, a button member 14, and first and second conductors 15, 16. Each of the conductor body 12 and the first and second conductors 15, 16 has a leg portion that extends out of the casing 11. The button member 14 is disposed in the casing 11 on top of the contact plate 13, and is operable so as to move the contact plate 13 from a first position, where the contact plate 13 connects the conductor body 12 and the first conductor 15, and a second position, where the contact plate 13 connects the conductor body 12 and the second conductor 16.
The conductor body 12 has a horizontal plate portion 121, a leg portion 122 extending integrally and downwardly from one end of the plate portion 121, and first and second mounting arms 123, 124 extending upwardly from two ends of the plate portion 121. The first and second mounting arms 123, 124 are formed with horizontal retaining grooves 1230, 1240. The retaining groove 1230 is disposed higher than the retaining groove 1240.
The contact plate 13 has an integral spring extension 132 formed within a longitudinal opening via a punching process, and a contact stub 131.
When the contact plate 13 is mounted on the conductor body 12, the first and second mounting arms 123, 124 extend through the longitudinal opening of the contact plate 13 and the retaining grooves 1230, 1240 engage one of the punched edges and the spring extension 132 respectively. At this time, the spring extension 132 is bent so as to bias the contact stub 131 to the first position.
During assembly, the first and second conductors 15, 16 are first secured to the casing 11. Due to space restrictions, the common conducting unit is assembled before being secured to the casing 11. Finally, the button member 14 is mounted to the casing 11 to complete assembly of the contact switch.
The drawback of the conventional conducting unit is as follows: The contact plate 13 is moved via the biasing force of the spring extension 132. The spring extension 132 is subject to breaking after long-term use.
To solve the above problem, referring to FIGS. 2 and 3, another conventional contact plate 23 is shown to include a main plate 231 and a separate spring plate 232 which is curved upward. The spring plate 232 has two horizontal ends 2321, 2322. When mounted on the conductor body 22, the spring plate 232 is moved upward relative to the main plate 231. The end 2321 of the spring plate 232 engages the second retaining groove 224 while the end 2322 abuts against a bottom surface of the main plate 231 immediately below an edge of the contact plate 23. However, there are still some drawbacks as follows: During assembly, the main and spring plates 231, 232 are first mounted on the conductor body 22 and are then mounted in the casing (not shown) of the contact switch. Since the spring plate 232 only abuts against the bottom surface of the main plate 231, it tends to be released downwardly from the latter although upward release movement can be prevented. After mounting the first and second conductors (not shown) and the conductor body 22 in the casing, the main and spring plates 231, 232 are mounted on the conductor body 22 from the top of the casing. Since the spring plate 232 is small, it is difficult to press and bend the small spring plate 232 to fit the same in the opening of the main plate 231 to engage the same with the conductor body 22.